Prospects for Detecting Neutral Hydrogen Using 21-cm Radiation from Large Scale Structure at High Redshifts
We estimate the signal from large scale structure at high redshifts in redshifted 21-cm line. We focus on z about 3 and the Lambda-CDM cosmology. We assume that neutral hydrogen is to be found only in galaxies, and normalize the total content to the density parameter of neutral hydrogen in damped Lyman alpha absorption systems (DLAS). We find that the rms fluctuations due to the large scale distribution of galaxies is very small and cannot be observed at angular scales probed by present day telescopes. We have used the sensitivity of the Giant Meter-wave Radio Telescope (GMRT) for comparison. We find that observations stretching over 10^3 hours will be required for a 3 sigma detection of such objects.